Hi Agent,
So this leads me to think that maybe your user has the Excel add-in installed in a different folder than your other users. I've seen this issue in older versions where a prefix showed up in front if XFGetCell (along with a long folder path to the add-in). Once we re-installed the add-in to the same folder as all other users, the issue was gone.
Now this may no longer be the case with the latest version of Excel and add-in but it's worth reviewing where the add-in is installed on your users computer versus everyone else.